Considerable thermal loading experienced by a turbine housing typically requires using comparatively expensive material. Accordingly, it may be desirable to provide a coolant system to limit the temperature of the turbine housing. However, adding too much heat to the coolant system may be undesirable with regard to other engine systems. In addition, it may be undesirable to cool the exhaust too much. Embodiments disclosed herein provide a thermal transfer mechanism that enables effective heat removal from the exhaust flow, while not overheating other engine systems, or overcooling the engine exhaust.
An internal combustion engine of the form, together with the cylinder liners and the cylinder head, the combustion chambers of the internal combustion engine.
The cylinder head may conventionally serves to hold the valve drives. To control the charge exchange, an internal combustion engine requires control elements and actuating devices for actuating the control elements. During the charge exchange, the exhaust gases are discharged via the outlet openings and the charging of the combustion chamber takes place via the inlet openings. To control the charge exchange, in four-stroke engines, use is made almost exclusively of lifting valves as control elements, which lifting valves perform an oscillating lifting movement during the operation of the internal combustion engine and which lifting valves open and close the inlet openings and outlet openings in this way. The valve actuating mechanism required for the movement of a valve, including the valve itself, is referred to as the valve drive.
Intake lines which lead to the inlet openings, and the exhaust lines which adjoin the outlet openings, may be at least partially integrated in the cylinder head. The merging of exhaust lines to form an overall exhaust line is referred to generally, and also within the context of the present invention, as an exhaust manifold.
Some engines may include an exhaust-gas turbocharger wherein downstream of the outlet openings, the exhaust gases may be supplied to at least one turbine. After the turbine the exhaust gases may pass through one or more exhaust-gas aftertreatment systems.
The production costs for the turbine can be comparatively high because the—nickel-containing—material often used for the thermally highly loaded turbine housing is expensive, in particular in relation to aluminum, which is preferably used for the cylinder head. It is not only the costs for the nickel-containing materials or for the nickel-containing cast steel per se but also the costs for machining these materials which may be comparatively high.
Accordingly, it follows that, with regard to costs, it would be highly advantageous if a turbine could be provided which can be manufactured from a less expensive material, for example gray iron or cast iron, in particular if taken into consideration that a close-coupled arrangement of the turbine is sought and often leads to a relatively large-dimensioned, voluminous housing. This may be because the connection of the turbine and cylinder head by means of a flange and screws may utilize a large turbine inlet region on account of the restricted spatial conditions, and may be because adequate space must be provided for the assembly tools. A voluminous housing can be associated with a correspondingly high level of material usage. The cost advantage is therefore particularly pronounced in the case of a turbine arranged close to the engine on account of the comparatively high material usage. The use of aluminum would have an additional advantage with regard to the weight of the turbine.
Using a cooling arrangement may enable use of cheaper materials. For example with a liquid-type cooling arrangement, which significantly may reduce the thermal loading of the turbine and of the turbine housing by the hot exhaust gases and may therefore permit the use of thermally less highly loadable materials.
In general, the turbine housing may be provided with a coolant jacket in order to form the cooling arrangement. Efforts have been made regarding both concepts wherein the housing is a cast part and the coolant jacket is jointly formed, during the casting process, as an integral constituent part of a monolithic housing, and also concepts in which the housing is of modular construction, wherein during assembly a cavity is formed which serves as a coolant jacket.
A turbine designed according to the latter concept is described for example in the German laid-open specification DE 10 2008 011 257 A1 (Also, WO2009106166 A1). A liquid-type cooling arrangement of the turbine is formed by virtue of the actual turbine housing being provided with a casing, such that a cavity into which coolant can be introduced is formed between the housing and the at least one casing element arranged spaced apart therefrom. The housing which is expanded to include the casing arrangement then comprises the coolant jacket.
The inventors herein have recognized a number of shortcomings with this approach. For example, on account of the high specific heat capacity of a liquid, in particular of water which is conventionally used, large amounts of heat may be extracted from the housing by means of liquid-type cooling. The heat may be dissipated to the coolant in the interior of the housing and may be discharged with the coolant. The heat which is dissipated to the coolant may be extracted from the coolant again in a heat exchanger. It is basically possible for the liquid-type cooling arrangement of the turbine to be equipped with a separate heat exchanger or else—in the case of a liquid-cooled internal combustion engine—for the heat exchanger of the engine cooling arrangement, that is to say the heat exchanger of a different liquid-type cooling arrangement, to be used for this purpose. The latter merely requires corresponding connections between the two circuits. In this context, it must be taken into consideration that the amount of heat to be absorbed by the coolant in the turbine may be so high that it may be a problem for said large amount of heat to be extracted from the coolant in the heat exchanger and discharged by way of an air flow to the surroundings.
Modern motor vehicle drives may be typically equipped with high-powered fan motors in order to provide, at the heat exchangers, the air mass flow required for an adequately high heat transfer. However, a further parameter which is significant for the heat transfer, specifically the surface area provided for the heat transfer, cannot be made arbitrarily large or enlarged arbitrarily because the space availability in the front-end region of a vehicle, in which the various heat exchangers are generally arranged, is limited.
Various concepts have been developed for limiting the amount of heat absorbed by the coolant in the turbine. The German laid-open specification DE 10 2011 002 554 A1 describes a concept in which, in the turbine housing, chambers are provided which are arranged between the exhaust gas-conducting flow duct of the turbine and the coolant duct and which function as a heat barrier, such that the heat flow from the exhaust gas or flow duct to the coolant duct and into the coolant is impeded and thereby reduced. By means of the structural design of the chambers, in particular the shaping, it is possible to influence the heat flows and thus the temperature distribution in the turbine housing.
The inventors herein have recognized problems with this approach well, for example in terms of manufacturing. The production of the chambers, which in some cases may also accommodate a process fluid, is problematic, in particular the removal of the cores required for the production process by way of casting. In some cases, a modular, that is to say multi-part, construction of the turbine housing may be inevitable.
Other concepts for limiting the amount of heat absorbed by the coolant restrict the spatial extent of the at least one coolant duct in the housing of the turbine or provide thermal insulation at the coolant side. One concept of the former type provides for example that the at least one coolant duct does not completely encase, that is to say surround, the impeller of the turbine—similarly to a coolant jacket—but rather extends over the flow duct in a circumferential direction only over a limited angle range α, where for example α≤45°.
Excessive cooling of the turbine or of the turbine housing furthermore may inevitably lead to corresponding considerable cooling of the exhaust gas that is conducted through the turbine. This however, may be fundamentally undesirable. Firstly, it is specifically sought to be able to optimally utilize the exhaust-gas enthalpy of the hot exhaust gases, which is determined significantly by the exhaust-gas temperature, for energy production. Secondly, the exhaust gas is generally subjected, downstream of the turbine, to exhaust-gas aftertreatment, and the exhaust-gas aftertreatment systems used require an adequately high exhaust-gas temperature for the conversion of the pollutants.
Embodiments in accordance with the present disclosure may provide an internal combustion engine is provided which may include a cylinder head, a turbine, and a turbine housing. The turbine housing may include an exhaust gas passage, at least one coolant fluid passage, and a wall between the passages. The wall may have a first area (Aexhaust) disposed to absorb heat from an exhaust flow passing through the exhaust gas passage, and a second area (Acoolant) disposed to transfer heat from the wall to be absorbed by a coolant fluid flow passing through the at least one coolant fluid passage, wherein the following applies: Acoolant/Aexhaust≤1.2.
The material through which heat may pass from the exhaust flow into the coolant flow may be conceptualized, in cross section, as a trapezoid wherein heat from the exhaust enters the material through the long base of the trapezoid, and heat leaves the material and enters the coolant through the short base of the trapezoid. However, this description should be understood as a conceptual model, and not necessarily limited to a strict trapezoidal shape. Either or both of the “bases” may be straight or curved, continuous or discontinuous. Similarly, Aexhaust and Acoolant may either, or both, be flat or having relief, continuous or discontinuous; and have relative sizes in accordance with the present disclosure.
In this way, the surface area exposed to coolant Acoolant of the liquid-type cooling arrangement of the turbine housing may be restricted in terms of size, that is to say is limited in terms of extent. This may serve for reducing or limiting the amount of heat absorbed, or to be absorbed, by the coolant. The size of the surface area exposed to coolant is a parameter of significance for the heat transfer, in particular for the heat transfer owing to convection.
Proceeding from the surface area exposed to exhaust gas Aexhaust of the turbine housing, such as may be present in individual cases and may be formed by the at least one exhaust-gas-conducting flow duct, the surface area exposed to coolant Acoolant of the at least one coolant duct may be sized to be no larger than 1.2 times the surface area exposed to exhaust gas. The surface area exposed to coolant of the housing cooling arrangement amounts to, for example, at most 120% of the surface area exposed to exhaust gas of the turbine housing.
By means of the structural design or shaping of the at least one exhaust-gas-conducting flow duct and of the at least one coolant duct, the area ratio and the number and arrangement thereof, it is possible to influence the amount of heat introduced into the coolant, but also the heat flows themselves and thus the temperature distribution in the turbine housing.
In the present case, it is not the aim to encase the at least one flow duct with coolant over the largest possible area and to thus realize the greatest possible dissipation of heat. Rather, through the limitation of the size of the surface area exposed to coolant Acoolant of the at least one coolant duct, the amount of heat to be dissipated may be reduced or limited. The problem of having to dissipate large amounts of heat absorbed by the coolant is thus mitigated.
Firstly, the turbine cooling arrangement according to various embodiments may make it possible to dispense with thermally highly loadable nickel-containing materials for producing, in particular, the turbine housing, because the thermal loading of the material may be reduced. Secondly, the cooling power is generally not sufficient to permit the use of materials that can be subjected to only low thermal loading, such as aluminum.
Correspondingly to the moderate cooling power, it may be advantageous, for the production of the liquid-cooled turbine according to the invention, to select a corresponding material, preferably gray iron or cast iron, if appropriate with additives such as for example silicon molybdenum (SiMo).
The turbine may be designed as a radial turbine, that is to say the flow approaching the impeller blades of the at least one impeller runs substantially radially. Here, “substantially radially” means that the speed component in the radial direction is greater than the axial speed component. The speed vector of the flow intersects the shaft or axle of the turbine, specifically at right angles if the approaching flow runs exactly radially. To make it possible for the impeller blades to be approached by flow radially, the at least one flow duct for the supply of the exhaust gas is often designed as an encircling spiral or volute housing, such that the inflow of exhaust gas to the turbine impeller runs substantially radially.
The turbine may however also be designed as an axial turbine, in which the speed component in the axial direction is greater than the speed component in the radial direction.
The above embodiments relating to the turbine encompass all structural forms of the mixed-flow turbine.
Embodiments of the internal combustion engine are advantageous in which a supercharging arrangement, preferably an exhaust-gas turbocharging arrangement, is provided.
In this context, embodiments are advantageous in which the at least one turbine is a constituent part of an exhaust-gas turbocharger. Owing to the relatively high exhaust-gas temperatures, a supercharged internal combustion engine is subject to particularly high thermal loads, for which reason cooling of the turbine of the exhaust-gas turbocharger is advantageous.
Supercharging serves primarily to increase the power of the internal combustion engine. Here, the air required for the combustion process is compressed, as a result of which a greater air mass can be supplied to each cylinder per working cycle. In this way, the fuel mass and therefore the mean pressure can be increased.
Supercharging is a suitable means for increasing the power of an internal combustion engine while maintaining an unchanged swept volume, or for reducing the swept volume while maintaining the same power. In any case, supercharging leads to an increase in volumetric power output and a more expedient power-to-weight ratio. If the swept volume is reduced, it is thus possible, given the same vehicle boundary conditions, to shift the load collective toward higher loads, at which the specific fuel consumption is lower. Supercharging consequently may assist in the constant efforts in the development of internal combustion engines to minimize fuel consumption, that is to say to improve the efficiency of the internal combustion engine.
The advantage of an exhaust-gas turbocharger in relation to a mechanical charger is that no mechanical connection for transmitting power is required between the charger and the internal combustion engine. While a mechanical charger draws the energy required for driving it directly from the internal combustion engine, the exhaust-gas turbocharger utilizes the exhaust-gas energy of the hot exhaust gases.
Embodiments of the internal combustion engine may include at least one cylinder head has at least two cylinders. If the cylinder head has two cylinders and only the exhaust lines of, or exhaust gases from, one cylinder open or issue into the turbine, this is likewise an internal combustion engine according to the invention.
In some cases the cylinder head has three or more cylinders, and the exhaust lines of two cylinders may lead into the turbine.
Embodiments in which the at least one cylinder head has, for example, four cylinders in an in-line arrangement and the exhaust lines of the outer cylinders and the exhaust lines of the inner cylinders merge to form in each case one overall exhaust line are likewise internal combustion engines according to the present disclosure. This may be the case specifically irrespective of whether the two overall exhaust lines open into the same turbine or separately from one another in each case into a separate turbine.
The at least one turbine may be a two-channel turbine. A two-channel turbine has an inlet region with two inlet ducts and two channels, with the two overall exhaust lines being connected to the two-channel turbine in such a way that in each case one overall exhaust line opens into one inlet duct or one channel.
Embodiments may also be advantageous in which the exhaust lines of all the cylinders of the at least one cylinder head may merge to form a single, that is to say common, overall exhaust line, which opens into the at least one turbine.
Embodiments of the internal combustion engine may be advantageous in which the following applies: Acoolant/Aexhaust≤1.0.
Embodiments of the internal combustion engine may be advantageous in which the following applies: Acoolant/Aexhaust≤0.8.
Embodiments of the internal combustion engine may be advantageous in which the following applies: Acoolant/Aexhaust≤0.65.
Embodiments of the internal combustion engine may be advantageous in which the following applies: Acoolant/Aexhaust≤0.55.
Embodiments of the internal combustion engine may be advantageous in which the following applies: Acoolant/Aexhaust≤0.50.
Embodiments of the internal combustion engine may be advantageous in which the following applies: Acoolant/Aexhaust≤0.48 or 0.45.
The above embodiments may make allowance for the fact that the area ratio Acoolant/Aexhaust duly may be selected so as to be fundamentally smaller in order to reduce the amount of heat introduced into the coolant, but should also be adapted to the respective individual situation or application. Here, the exhaust-gas flow rate and the exhaust-gas temperature have a significant influence on the area ratio that can be realized.
Embodiments of the internal combustion engine are advantageous in which at least one additional coolant duct may lead through a housing tongue that forms the turbine housing at the end of the at least one exhaust-gas-conducting flow duct. The housing tongue, which may constitutes or may jointly form the end of the exhaust-gas-conducting flow duct and which may extend to a point as close as possible to the rotating impeller, is the thermally most highly loaded region of the turbine housing. There may be numerous reasons for this. At least in the case of radial turbines, a part of the exhaust gas passes the housing tongue twice, specifically firstly upon entering the turbine housing, that is to say at the inlet into the exhaust-gas-conducting flow duct which extends in ring-shaped fashion around the impeller, and a second time upon finally entering the rotating impeller at the end of the flow duct. Consequently, the housing tongue may be exposed to hot exhaust gas on both sides, wherein the heat introduced into the tongue by the exhaust gas can be dissipated by heat conduction basically only via a narrow web by which the tongue is connected to the turbine housing itself. The tongue may be thermally loaded by the hot exhaust-gas flow not only on both sides but also at its free end which faces the impeller and which is likewise exposed to hot exhaust gas.
Furthermore, the exhaust-gas flow may be diverted with greater or lesser intensity by the housing tongue in order to conduct the exhaust gas to the impeller. Here, the exhaust-gas flow strikes the housing tongue and has a speed component which is perpendicular to the wall of the tongue, whereby the heat transfer by convection, and consequently the thermal loading of the housing tongue, are increased.
If at least one additional coolant duct is provided, embodiments may be advantageous in this context in which the at least one additional coolant duct runs substantially parallel to the shaft of the turbine. The additional coolant duct may be formed into the housing during the course of a finish machining process, for example by way of drilling, and then runs preferably rectilinearly. The surface area exposed to coolant of the at least one additional coolant duct may also incorporated into the area ratio Acoolant/Aexhaust.
Embodiments of the internal combustion engine are advantageous in which at least one bypass line is provided which branches off from at least one exhaust gas-conducting flow duct upstream of the at least one impeller.
The configuration of the exhaust-gas turbocharging may include difficulties, wherein it is basically sought to obtain a noticeable performance increase in all engine speed ranges. However, a torque drop is observed in the event of a certain engine speed being undershot. Said torque drop is understandable if one takes into consideration that the charge pressure ratio is dependent on the turbine pressure ratio. For example, if the engine speed is reduced, this leads to a smaller exhaust-gas mass flow and therefore to a lower turbine pressure ratio. This has the result that, toward lower engine speeds, the charge pressure ratio and the charge pressure likewise decrease, which equates to a torque drop.
It is sought, using a variety of measures, to improve the torque characteristic of a supercharged internal combustion engine. This maybe achieved, for example, by means of a small design of the turbine cross section and simultaneous provision of an exhaust-gas blow-off facility. Such a turbine is also referred to as a wastegate turbine. If the exhaust-gas mass flow exceeds a critical value, a part of the exhaust-gas flow is, within the course of the so-called exhaust-gas blow-off, conducted via the bypass line past the turbine. Said approach however has the disadvantage that the supercharging behavior is inadequate at relatively high engine speeds or in the case of relatively high exhaust-gas flow rates.
The torque characteristic may also be advantageously influenced by means of multiple exhaust-gas turbochargers connected in series. By connecting two exhaust-gas turbochargers in series, of which one exhaust-gas turbocharger serves as a high-pressure stage and one exhaust-gas turbocharger serves as a low-pressure stage, the compressor characteristic map can advantageously be expanded, specifically both in the direction of smaller compressor flows and also in the direction of larger compressor flows.
In particular, with the exhaust-gas turbocharger which serves as a high-pressure stage, it is possible for the surge limit to be shifted in the direction of smaller compressor flows, as a result of which high charge pressure ratios can be obtained even with small compressor flows, which considerably improves the torque characteristic in the lower engine speed range. This is achieved by designing the high-pressure turbine for small exhaust-gas mass flows and by providing a bypass line by means of which, with increasing exhaust-gas mass flow, an increasing exhaust-gas flow rate is conducted past the high-pressure turbine. For this purpose, the bypass line branches off from the exhaust-gas discharge system upstream of the at least one impeller of the high-pressure turbine and opens into the exhaust-gas discharge system again upstream of the low-pressure turbine, wherein a shut-off element is arranged in the bypass line in order to control the exhaust-gas flow conducted past the high-pressure turbine. The response behavior of an internal combustion engine supercharged in this way it may be considerably improved in relation to a similar internal combustion engine with single-stage supercharging, because the rotor of an exhaust-gas turbocharger of smaller dimensions can be accelerated more quickly, whereby the relatively small high pressure stage is less inert.
It is pointed out that the torque characteristic of a supercharged internal combustion engine may furthermore be improved by means of multiple turbochargers arranged in parallel, that is to say by means of multiple turbines of relatively small turbine cross section arranged in parallel, wherein turbines are activated successively with increasing exhaust-gas flow rate.
If a bypass line is provided, embodiments of the internal combustion engine may be advantageous in this context in which the at least one bypass line opens into the exhaust-gas discharge system downstream of the at least one impeller. Simply with regard to common exhaust-gas aftertreatment, a merging of the bypassed exhaust gas with the rest of the exhaust gas that has been conducted through the turbine is expedient and advantageous.
In this context, embodiments of the internal combustion engine may in turn be advantageous in which the at least one bypass line opens into an outlet region of the turbine. This makes it possible to realize a compact construction of the turbine unit as a whole together with bypass line.
In this context, embodiments of the internal combustion engine may also be advantageous in which the at least one bypass line is cooled at least in regions using the cooling arrangement. The bypass line and in particular the shut-off element provided in the bypass line are thermally highly loaded components. In the case of the shut-off element, the cooling arrangement serves in particular for maintaining the functionality of the shut-off element.
Embodiments of the internal combustion engine may be advantageous in which the shaft of the turbine is mounted in a bearing housing, wherein the bearing housing has at least one coolant duct on the impeller side. The liquid-cooled bearing housing supplements and supports the cooling arrangement of the turbine housing.
In the case of internal combustion engines in which the turbine has a turbine inlet region and/or a turbine outlet region, embodiments are advantageous wherein thermal insulation is provided, at the exhaust-gas side and at least in regions, in the turbine inlet region and/or in the turbine outlet region.
In the context of the present disclosure, the turbine inlet region and the turbine outlet region may belong to the turbine housing and thus also to the turbine.
The walls that form the turbine inlet region and turbine outlet region delimit the exhaust-gas discharge system at the inlet side and at the outlet side and may be—at least in regions—equipped with, that is to say coated, lined, surface-treated or the like, with thermal insulation. In the context of the present invention, thermal insulation may be distinguished from the housing material that is used very generally by the fact that the thermal insulation exhibits lower thermal conductivity than said material. The thermal permeability of the heat-transmitting surface, that is to say of the walls, is reduced, wherein it is the case, that heat can basically be introduced, this however being so to a lesser extent.
In the present case, the introduction of heat into the turbine at the inlet side and outlet side may be impeded by the introduction of thermal insulation, such that in individual cases, it is possible, though not imperative, for a cooling arrangement of the turbine inlet region and turbine outlet region to be dispensed with. Embodiments of the internal combustion engine may therefore also be advantageous in which the turbine inlet region and the turbine outlet region do not have a cooling arrangement or a coolant duct.
Embodiments of the internal combustion engine may be advantageous in which the turbine housing together with the at least one coolant duct and the at least one flow duct is a component cast in one piece. In individual cases, the turbine inlet region and the turbine outlet region likewise belong to the component of monolithic form; possibly also a wastegate.
By means of casting and the use of corresponding cores, a complex structure can be formed in one working step, such that subsequently only finish machining and the installation of the rotor are necessary in order to form the turbine. The advantages of a component of monolithic form as per the embodiment in question are in particular the compact construction and the omission of additional assembly working steps and the like. In this way, the monolithic component to be manufactured from gray iron or cast iron.
Embodiments of the internal combustion engine may also be advantageous in which the turbine housing together with the at least one coolant duct and the at least one flow duct is constructed in modular fashion from at least two components, that is to say is of multi-part form.
A modular construction in which at least two components are to be connected to one another has the basic advantage that the individual components can be used in different embodiments according to the construction kit principle. The versatility of a component generally increases the quantities produced, as a result of which the manufacturing costs can be reduced. The at least two components may be connected to one another in non-positively locking, positively locking and/or cohesive fashion.
Embodiments of the internal combustion engine are advantageous in which each cylinder may have two or three outlet openings for discharging the exhaust gases out of the cylinder.
It is the object of valve drives to open and close the outlet openings of the cylinders at the correct times, with fast opening of the largest possible flow cross sections being sought in order to keep the throttling losses in the outflowing exhaust gases low and in order to ensure effective, that is to say complete, discharge of the exhaust gases. It is therefore advantageous for the cylinders to be provided with two or more outlet openings.
Embodiments of the internal combustion engine may be advantageous in which the exhaust lines merge to form at least one overall exhaust line within the at least one cylinder head, thus forming at least one integrated exhaust manifold.
It may be taken into consideration that it is fundamentally sought to arrange the at least one turbine, in particular the turbine of an exhaust-gas turbocharger, as close as possible to the outlet of the cylinders in order thereby to be able to optimally utilize the exhaust-gas enthalpy of the hot exhaust gases, which is determined significantly by the exhaust-gas pressure and the exhaust-gas temperature, and to ensure a fast response behavior of the turbine or of the turbocharger. Furthermore, the path of the hot exhaust gases to the different exhaust-gas aftertreatment systems should also be as short as possible such that the exhaust gases may be given little time to cool down and the exhaust-gas aftertreatment systems reach their operating temperature or light-off temperature as quickly as possible, in particular after a cold start of the internal combustion engine.
It is therefore also sought to minimize the thermal inertia of the part of the exhaust line between the outlet opening at the cylinder and the turbine or between the outlet opening at the cylinder and the exhaust-gas aftertreatment system, which can be achieved by reducing the mass and the length of said part.
The exhaust lines may merge within the cylinder head so as to form at least one integrated exhaust manifold. The length of the exhaust lines may be reduced in this way. The line volume, that is to say the exhaust-gas volume of the exhaust lines upstream of the turbine, is reduced, such that the response behavior is improved. The shortened exhaust lines also lead to a reduced thermal inertia of the exhaust system upstream of the turbine, such that the temperature of the exhaust gases at the turbine inlet is increased, as a result of which the enthalpy of the exhaust gases at the inlet of the turbine is also higher. Furthermore, the merging of the exhaust lines within the cylinder head permits dense packaging of the drive unit.
However, a cylinder head with an integrated exhaust manifold may be thermally more highly loaded than a conventional cylinder head which is equipped with an external manifold, and may therefore place greater demands on the cooling arrangement. Embodiments of the internal combustion engine may be therefore also advantageous in which the at least one cylinder head is provided with at least one coolant jacket, which is integrated in the cylinder head, in order to form a liquid-type cooling arrangement.
A liquid-type cooling arrangement may be advantageous in particular in the case of supercharged engines because the thermal loading of supercharged engines is considerably higher than that of conventional internal combustion engines.
In this context, embodiments of the internal combustion engine may be advantageous in which the at least one coolant jacket that is integrated in the cylinder head is connected to at least one coolant duct of the turbine housing.
If the at least one coolant jacket which is integrated in the cylinder head is connected to the at least one coolant duct of the turbine housing, the other components and assemblies required to form a cooling circuit need basically be provided only singularly, as these may be used both for the cooling circuit of the turbine housing and also for that of the internal combustion engine, which may lead to synergies and cost savings, but also entails a weight saving.
For example, it is preferable for only one pump for conveying the coolant, and one container for storing the coolant, to be provided. The heat dissipated to the coolant in the cylinder head and in the turbine housing can be extracted from the coolant in a common heat exchanger. Furthermore, the at least one coolant duct of the turbine housing may be supplied with coolant via the cylinder head.
Embodiments of the internal combustion engine are advantageous in which at least one coolant duct in the turbine housing runs, at least in sections, in looped fashion around the shaft. In the present case, a coolant duct need not form a complete loop, but rather may form merely a section of a loop or more, that is to say at least one arcuate section which lies or extends circumferentially around the shaft of the turbine; if appropriate on a circular arc.
Embodiments of the internal combustion engine may also be advantageous in which at least one coolant duct runs, at least in sections, to the side of at least one exhaust-gas-conducting flow duct and so as to be spaced apart from said flow duct in the direction of the shaft. Here, a coolant duct may also change sides, that is to say may run laterally with respect to the exhaust-gas-conducting flow duct and then lead across the flow duct to the other side of the flow duct, in order to extend onward there laterally with respect to the flow duct. The coolant duct and the flow duct are preferably spaced apart to the same extent from the shaft.
Embodiments of the internal combustion engine may be advantageous in which at least one coolant duct extends, at least in sections, circumferentially around and so as to be spaced apart from at least one flow duct. The coolant duct and the flow duct are then, at least in sections, spaced apart to different extents from the shaft. Embodiments may also be advantageous in which at least two coolant ducts are provided for forming a cooling arrangement of the turbine housing.
The provision of more than one coolant duct is conducive to the homogenization of the temperature distribution in the housing, that is to say to a depletion of the temperature gradients and stresses that arise in the housing out of principle in conjunction with a cooling arrangement. The turbine may be equipped with a variable turbine geometry, which permits a more precise adaptation to the respective operating point of an internal combustion engine by means of an adjustment of the turbine geometry or of the effective turbine cross section. Here, adjustable guide blades for influencing the flow direction are arranged in the inlet region of the turbine. In contrast to the impeller blades of the rotating impeller, the guide blades do not rotate with the shaft of the turbine.
If the turbine has a fixed, invariable geometry, the guide blades are arranged in the inlet region so as to be not only stationary but rather also completely immovable, that is to say rigidly fixed, if a guide device is provided. In contrast, in the case of a variable geometry, the guide blades are duly arranged so as to be stationary but not so as to be completely immovable, rather so as to be rotatable about their axis, such that the flow approaching the impeller blades can be influenced.
By contrast to a fixed, invariable geometry, a variable turbine geometry is even less thermally loadable owing to the movable components, whereby the cooling of a turbine that is equipped with a variable turbine geometry is particularly advantageous.